In that case, I'd probably install a Variable AC-DC power supply and run the smoke unit and fan off of that. You can use a series resistor for the fan to vary it's speed to get the effect you desire using the same DC output. Truthfully, for a diner, I'd use a larger smoke unit with a bigger fluid reservoir so you would have to fill it less often.
I've put a couple of the HO units in cabooses, they have the right level of output for a caboose.
